Electrification of aviation is regarded as one of the means to make aircraft operations less polluting and to have lower climate impact. Yet, air transportation's environmental impact depends on power train technologies and novel designs and aircraft operations within airline networks. Fully- or hybrid-electric aircraft may enter existing air transport networks through fleet replacement yet require airlines to adapt in order to operate electrified aircraft strategically. This research studies how airlines can strategically adjust their network and fleet composition when considering electrified aircraft. The novelty of this approach is to provide a direct feedback coupling between fleet planning, conceptual hybrid-electric aircraft design and climate impact minimization. Therefore, a strategic airline planning model, consisting of fleet and network analysis, is coupled to a hybrid-electric aircraft design model. A case study on the sensitivity of a regional airline network is presented to demonstrate the framework and assess the impact of trying to design aircraft and fleets with minimal climate footprint. A decrease in emissions with respect to a kerosene fleet of 11% can be achieved when a hybrid-electric fleet is designed particularly for the specified network, at the penalty of a profit decrease of 13%. Limiting fleet diversity to three types results in only 7% emissions decrease. Increasing the battery-specific energy shows an expected beneficial effect on emissions.